Fisiologia Vegetal
URI permanente para esta coleçãohttps://locus.ufv.br/handle/123456789/185
Navegar
6 resultados
Resultados da Pesquisa
Item Importância fisiológica dos transportadores mitocondriais de adenilatos AACs em Arabidopsis thaliana(Universidade Federal de Viçosa, 2019-03-11) Batista, Amanda Lima; Nesi, Adriano Nunes; http://lattes.cnpq.br/5734266643442378A mitocôndria é a organela responsável pela maior parte do fornecimento do ATP necessário para os processos metabólicos de manutenção do crescimento e respostas a vários estresses. O transporte de adenilatos (AMP, ADP e ATP) através da membrana mitocondrial interna é mediado por proteínas carreadoras especializadas, dentre as quais se encontram os carreadores do tipo antiporte ADP/ATP (AAC), que exportam o ATP para o citosol e, simultaneamente, importam o ADP para a matriz mitocondrial. Em Arabidopsis thaliana, são encontradas as isoformas AAC1, AAC2 e AAC3, cujos papeis fisiológicos ainda permanecem desconhecidos. Neste trabalho, avaliou-se em Arabidopsis thaliana o papel dos transportadores mitocondriais de ADP/ATP, denominados AtAAC1, AtAAC2 e AtAAC3. Para tal, foram utilizadas linhagens mutantes homozigotas com baixa expressão obtidas por inserção do T-DNA. Estas plantas foram caracterizadas a nível fisiológico e bioquímico. A análise do padrão de expressão dos genes AACs em plantas selvagens em condições ideais de cultivo demonstrou que de fato eles provavelmente desempenham papeis fisiológicos distintos em função do tecido e estágio do desenvolvimento. O gene AAC1 se apresentou como a isoforma mais abundante, independente do tecido e estágio do desenvolvimento. O AAC2 e o AAC3 tiveram expressão mais relevante em tecidos relacionados à fase reprodutiva, tais como grãos de pólen, flores e síliquas. Análise da expressão demonstrou que, na ausência do gene AAC2, ocorre regulação positiva dos demais transportadores de adenilatos da célula. Os mutantes para os genes AAC1, AAC2 e AAC3 exibiram maiores taxas de respiração noturna em relação a plantas WT sem apresentarem alterações na assimilação líquida de carbono e no crescimento. Adicionalmente, a quantificação metabólica nas plantas mutantes das três isoformas apontou tendência de maior acúmulo nos teores de aminoácidos, proteínas, glicose, frutose, sacarose e amido ao longo do período luminoso e alto consumo dos mesmos durante o período noturno. Também foram observadas maiores razões de poder redutor [NAD(P)H/NAD(P) + ] em mutantes para o gene AAC1, AAC2 e AAC3 comparado ao WT. Tomados em conjunto, os resultados sugerem que, esses transportadores ADP/ATP estão envolvidos principalmente no metabolismo do processo respiratório, balanço redox e concentrações de metabólitos nitrogenados e carbonados. Assim, pode-se sugerir que a dinâmica distribuição das moléculas de adenilato, promovida por estes transportadores, tenha vipapeis relevantes na sincronia entre o metabolismo diurno e noturno em plantas, contribuindo assim para a manutenção do steady-state celular, por mecanismos que precisam ser investigados. Para tal, é necessário, aprofundar a compressão do papel destes transportadores nos tecidos vegetais e condições adversas bem como o papel de enzimas chave que atuam no processo.Item Role of mitochondrial thioredoxin for redox regulation in the metabolism of Arabidopsis Thaliana(Universidade Federal de Viçosa, 2017-03-16) Pereira, Paula da Fonseca; Nesi, Adriano Nunes; http://lattes.cnpq.br/6419216674405263Redox-dependent changes substantially influence the functional activity of several proteins and participate in the regulation of the most vital cellular processes. Accordingly, thioredoxins (Trxs), small proteins containing a redox active disulfide group within its catalytic domain, have a fundamental role in the regulation of the redox environment of the cell. In plants, Trxs were early identified as mediators between light-driven electron transport and dark carbohydrate metabolism in chloroplasts. In other cell compartments than plastids, and in particular mitochondria, a growing body of information concerning Trx redox regulation has been obtained with the advent of proteomics and mass spectrometry-based techniques. Extraplastidial Trx system is comprised of two highly similar isoforms of NADPH-dependent Trx reductase, A and B, that are encoded by two distinct genes in Arabidopsis, whose gene products are denominated NTRA and NTRB and are both target to cytosol and mitochondria. The extraplastidial Trx system is also composed of several Trx h (in the cytoplasm) or Trx h and o in mitochondria which are, in turn, reduced by NTRA and NTRB. Previous studies showed that, in contrast to ntra and ntrb single knockout mutants, which show no visible phenotypic modifications under normal conditions, the double ntra ntrb mutant exhibit major modification differences. Previous studies have provided a significant contribution to our understanding of the TRX system in plants; however, the metabolic impact of this system has not been comprehensively evaluated. In order to gain more insight into the physiological and metabolic function of TRX system, the present study aimed to investigate the functional significance of Trx in cytosol and mitochondria by using an extensive steady state metabolic characterization of T-DNA insertional lines in Arabidopsis thaliana. That being said, here we focused on the investigation of the functional roles of TRXs in response to stress conditions and how Trxs and the regulated pathways interact to adjust to different cellular and metabolic requirements under normal growth conditions or following stress. In brief, the results presented here provided several novel findings and generated, at least preliminary, mechanistic interpretation of the impact of redox regulation on plant growth and carbon central metabolism. First, we characterized ntra ntrb double knockout mutant and two lines of the mitochondrial AtTRX-o1 subjected to multiple drought episodes. Our results indicate that Trx mutant plants are able to better cope with drought stress, which is probably linked with a lower energetic expenditure that would allow a faster recover in Trx mutants. In addition, we demonstrated the existence of a drought memory in plants by examining differential acclimative mechanisms associated with drought tolerance in Trx mutants of the mitochondrial Trx pathway in Arabidopsis. Moreover, it seems likely that this differential acclimation involves the participation a set of metabolic changes as well as redox poise alteration following recovery. The main results indicate that prior drought exposure is able to affect the subsequent response, indicating the occurrence of stress memory in drought stressed Arabidopsis plants. In addition, by evaluating physiological and metabolic responses of ntra ntrb and trxo1 mutants following high CO 2 enrichment and by the characterization of mitochondrial trxh2 knockout mutants, we demonstrate several evidences suggesting the importance of redox regulation by mitochondrial Trxs on stomatal function. Collectively, our data suggest a significant modulation of stomatal function by organic acids at high CO 2 in Trx mutants and, at the same time, they demonstrate that elevated CO 2 partly restored the metabolic response, including the intermediates of the TCA cycle, in Trx mutants. Overall, the results obtained are discussed both in terms of the importance of Trx for redox regulation in plant cell metabolism and with regard to the contribution that it plays in terms of total cellular homeostasis. The results discussed here not only provide important insight into the role of mitochondrial Trx system on the TCA cycle but also present a roadmap by which the role of Trx in the regulation of other key metabolic reactions of the mitochondria.Item Functional analysis of the thioredoxin system during seed germination in Arabidopsis thaliana(Universidade Federal de Viçosa, 2019-03-29) Nascimento, Carolina Pereira; Nesi, Adriano Nunes; http://lattes.cnpq.br/3331610618877369A series of processes occurs during seed formation, including remarkable changes from early development to the end of germination. The changes associated with processes initiated mainly after seed imbibition are usually characterized by extensive changes in redox state of seed reserve proteins and of pivotal enzymes for protein mobilization and usage. Such changes in redox state are often mediated by Thioredoxins (Trxs), which are protein oxiredutases capable of catalyzing the reduction of disulfide bonds in target proteins, thereby regulating their structure and function. Here, we analyzed the previously characterized mutants of NADPH-dependent Trx reductase A and B (ntra ntrb), two independent mutant lines of mitochondrial thioredoxin o1 (trxo1) and two mutant thioredoxin h2 (trxh2) mutant lines. Our results indicate that plants deficient for the NADPH-dependent thioredoxin system are able to mobilize their reserves, but at least partially fail to use these reserves during germination, thereby leading to lower availability of energy substrates than wild type seeds. Trx mutants also show decreased activity of regulatory systems needed to maintain cellular homeostasis. Moreover, we observed reduced respiration in mutant seeds and seedlings, which in parallel with an impaired energy metabolism, disrupts core biological processes responsible for proper germination and early development of Trx mutants. In conclusion, the results suggest that the lack of thioredoxin induces a substantial adaptation in seeds and seedlings, which undergo a metabolic reprogramming to adapt to a new redox state.Item Importância fisiológica dos Transportadores Mitocondriais de Adenilatos AACs em Arabidopsis thaliana(Universidade Federal de Viçosa, 2019-03-11) Batista, Amanda Lima; Nesi, Adriano Nunes; http://lattes.cnpq.br/5734266643442378A mitocôndria é a organela responsável pela maior parte do fornecimento do ATP necessário para os processos metabólicos de manutenção do crescimento e respostas a vários estresses. O transporte de adenilatos (AMP, ADP e ATP) através da membrana mitocondrial interna é mediado por proteínas carreadoras especializadas, dentre as quais se encontram os carreadores do tipo antiporte ADP/ATP (AAC), que exportam o ATP para o citosol e, simultaneamente, importam o ADP para a matriz mitocondrial. Em Arabidopsis thaliana, são encontradas as isoformas AAC1, AAC2 e AAC3, cujos papeis fisiológicos ainda permanecem desconhecidos. Neste trabalho, avaliou-se em Arabidopsis thaliana o papel dos transportadores mitocondriais de ADP/ATP, denominados AtAAC1, AtAAC2 e AtAAC3. Para tal, foram utilizadas linhagens mutantes homozigotas com baixa expressão obtidas por inserção do T-DNA. Estas plantas foram caracterizadas a nível fisiológico e bioquímico. A análise do padrão de expressão dos genes AACs em plantas selvagens em condições ideais de cultivo demonstrou que de fato eles provavelmente desempenham papeis fisiológicos distintos em função do tecido e estágio do desenvolvimento. O gene AAC1 se apresentou como a isoforma mais abundante, independente do tecido e estágio do desenvolvimento. O AAC2 e o AAC3 tiveram expressão mais relevante em tecidos relacionados à fase reprodutiva, tais como grãos de pólen, flores e síliquas. Análise da expressão demonstrou que, na ausência do gene AAC2, ocorre regulação positiva dos demais transportadores de adenilatos da célula. Os mutantes para os genes AAC1, AAC2 e AAC3 exibiram maiores taxas de respiração noturna em relação a plantas WT sem apresentarem alterações na assimilação líquida de carbono e no crescimento. Adicionalmente, a quantificação metabólica nas plantas mutantes das três isoformas apontou tendência de maior acúmulo nos teores de aminoácidos, proteínas, glicose, frutose, sacarose e amido ao longo do período luminoso e alto consumo dos mesmos durante o período noturno. Também foram observadas maiores razões de poder redutor [NAD(P)H/NAD(P)+] em mutantes para o gene AAC1, AAC2 e AAC3 comparado ao WT. Tomados em conjunto, os resultados sugerem que, esses transportadores ADP/ATP estão envolvidos principalmente no metabolismo do processo respiratório, balanço redox e concentrações de metabólitos nitrogenados e carbonados. Assim, pode-se sugerir que a dinâmica distribuição das moléculas de adenilato, promovida por estes transportadores, tenha papeis relevantes na sincronia entre o metabolismo diurno e noturno em plantas, contribuindo assim para a manutenção do steady-state celular, por mecanismos que precisam ser investigados. Para tal, é necessário, aprofundar a compressão do papel destes transportadores nos tecidos vegetais e condições adversas bem como o papel de enzimas chave que atuam no processo.Item The molecular functions of auxin signaling in tomato (Solanum lycopersicum L.)(Universidade Federal de Viçosa, 2018-03-02) Silva, Willian Batista; Araújo, Wagner Luis; http://lattes.cnpq.br/7187216024327321The auxin is a phytohormone with intense participation in the growth and development process, as well as in crucial physiological processes to the plant establishment. Although its role in development control is already well established and has been extensively investigated, in our understanding, little or nothing is currently known about the impacts on the manipulation of the signaling levels of this hormone in the metabolic impact, as well as the link between auxin and photosynthetic and respiratory process both in leaves and fruit. In this vain, considering the metabolic importance in plant and the wide regulatory network of this system, in this thesis initially I present a review offering an important comparative complement of post-genomic strategies, such as the profile of the metabolites, providing information on the regulation of the metabolic network and thus allowing a more complete description of the cellular function of the plant. A comparative analysis was made by raising a question, if stable isotope mass spectrometry could replace radiolabelled approaches in metabolic studies? In addition, to better understand the functions of the modulation of auxin perception levels and how it conducts metabolic adjustments in different plant tissues, two experimental approaches were adopted for: (i) Characterize tomato plants with alterations in auxin signaling balance and their modulations in primary metabolism in tomato leaves and (ii) to analyze the role of auxin signaling in the ripening of tomato fruits. Briefly, the results indicate that auxin acts as an integrator of metabolism and adjustment and suggests that altered perceptions of this hormone affect the chloroplastic and mitochondrial metabolism in lighted leaves, suggesting a great participation of this phytohormone in the final productivity determination. Moreover, at the fruit level, auxin seems to control metabolic alterations very little, but controlling important steps in fruit maturation, controlling the metabolism of starch and sugars, providing new perspectives of integration between auxin and respiratory paths.Item Functional analysis of mitochondrial proteins in Arabidopsis thaliana(Universidade Federal de Viçosa, 2016-08-26) Brito, Danielle Santos; Nesi, Adriano Nunes; http://lattes.cnpq.br/3177036222169807Mitochondrial carrier family (MCF) proteins catalyze the specific transport of various substrates, such as nucleotides, amino acids and cofactors. Although some of the mitochondrial transporters have been identified, many of these proteins have not yet been completely characterized. Likewise, the proteic machinery and mechanisms involved in the mitochondrial alternative respiration is still not well known. In this context, this work first presents a study of a previously identified but uncharacterized mitochondrial transporter AtSFC1, a potential succinate/fumarate carrier. Hence, to obtain the biochemical role of AtSFC1, we carried out substrate specificity and investigated its physiological function using 35S antisense transgenic lines in Arabidopsis thaliana. Briefly, the functional integration of AtSFC1 in the cytoplasmic membrane of intact Escherichia coli cells reveals a high specificity for a citrate/isocitrate in a counter exchange mode. Additionally, we discussed the potential role for AtSFC1 in the provision of intermediates of tricarboxylic acid cycle to provide carbon and energy to support growth in heterotrophic tissues. In the second part of this thesis, we investigated the function of alternative electron donors to the mitochondrial electron transport chain (mETC) during carbon deprivation as well as after the supply of amino acids. The breakdown products of branched chain amino acids can provide electrons to the mETC via the ETF/ETFQO (electron transfer flavoprotein: flavoprotein ubiquinone oxidoreductase) complex. This system is located in the mitochondria and induced at the level of transcription during stress situations. Thus, in order to obtain a comprehensive picture of how alternative respiration pathway interacts with other pathways and adjust to different cellular and metabolic requirements, we performed metabolic and physiological approaches using Arabidopsis cell culture ETFQO T-DNA insertion mutants. The results discussed here support that the ETF/ETFQO system is an essential pathway able to donate electrons to the ubiquinone pool. In addition, the behavior of the respiratory complexes suggest new electrons entry points, which must be elucidated.